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The study by Columbia University followed 60 newborns and their non-smoking mothers in low-income neighborhoods, primarily in Harlem and the Bronx.

Their exposure to combustion-related pollutants caused primarily by vehicles was measured by backpack air monitors worn by the women during the third trimester of their pregnancies.

When the babies were born, genetic alterations were measured. Researchers found about a 50 percent increase in the level of persistent genetic abnormalities in the infants who had the higher levels of exposure, said Dr. Frederica Perera, director of the center and senior author of the study.

“We already knew that air pollutants significantly reduced fetal growth, but this is the first time we’ve seen evidence that they can change chromosomes in utero,” Perera said.

She said the kind of genetic changes that occurred have been linked in other studies to increased risk of cancer.

“While we can’t estimate the precise increase in cancer risk,” Perera said, the findings underscore the need for government to take steps to protect children.

The study, published in the journal Cancer Epidemiology Biomarkers and Prevention, is part of a broader multi-year research project started in 1998 that examines the health effects of exposure of pregnant women and babies to air pollutants, pesticides and tobacco smoking.

James Quinn, a biologist at McMaster University in Ontario, Canada, who was one of the authors of an earlier study that examined pollution-related mutations in mice, said the Columbia study merits attention.

“This study adds to a growing list of studies suggesting that anthropogenic air pollution carries health risks and genetic consequences that may affect the next generation,” Quinn said in an e-mail.

Although the research isn’t conclusive and leaves open other possible causes for the genetic changes, Quinn said, the pollutants were “a likely explanation for the elevated anomalies. Presumably there will be follow-up experimental work.”

Christopher Somers, a research associate at the University of Regina who was another author of the mouse study, said, “The fact that the simple act of an expectant mother breathing might cause chromosome abnormalities in her unborn child is cause for concern.”